Isolation, characterization and reactivity of key intermediates relevant to reductive (electro)catalysis with Cp*Rh complexes containing pyridyl‐MIC (MIC=mesoionic carbene) ligands

Abstract

In recent years, metal complexes of pyridyl‐mesoionic carbene (MIC) ligands have been reported as excellent homogeneous and molecular electrocatalysts. In combination with group 9 metals, such ligands form highly active catalysts for hydrogenation/transfer hydrogenation/hydrosilylation catalysis and electrocatalysts for dihydrogen production. Despite such progress, very little is known about the structural/electrochemical/spectroscopic properties of crucial intermediates for such catalytic reactions with these ligands: solvato complexes, reduced complexes and hydridic species. We present here a comprehensive study involving the isolation, crystallographic characterization, electrochemical/spectroelectrochemical/theoretical investigations, and in‐situ reactivity studies of all the aforementioned crucial intermediates involving Cp*Rh and pyridyl‐MIC ligands. A detailed mechanistic study of the precatalytic activation of [RhCp*] complexes with pyridyl‐MIC ligands is presented. Intriguingly, amphiphilicity of the [RhCp*]‐hydride complexes was observed, displaying the substrate dependent transfer of H+, H or H-. To the best of our knowledge, this study is the first of its kind targeting intermediates and reactive species involving metal complexes of pyridyl‐MIC ligands and investigating the interconversion amongst them.